Map displaying method and apparatus, and navigation system having the map displaying apparatus

ABSTRACT

The present invention is related to a stereoscopic map displaying method beneficial for a navigation system in which map information is selected from a map database according to a current location of a mobile object. The map database for storing map information comprises a plurality of types of information regarding a first map mesh provided with height information and a second map mesh with no height information wherein there is provided information for identifying that the second map mesh has no height information.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is related to a map displaying method andapparatus, and a navigation system having such a map displayingapparatus. Particularly, the present invention is related to astereoscopic map displaying method beneficial for the navigation systemin which map information is selected from a map database according to acurrent location of a mobile object such as an automobile, and aperspective map viewing the ground surface along a direction angled tothe ground surface is displayed.

[0003] 2. Description of Related Art

[0004] The navigation system is known as an apparatus which assists adriver of an automobile by fetching digital map data stored in storagemedia such as CD-ROM, displaying a map showing buildings, roads and thelike on a display screen, and superposing a current location of theautomobile and a direction toward its destination on the map, which aredetected by various sensors such as GPS.

[0005] A recent navigation system, such as disclosed in Japanese PatentApplication Publication (KOKAI) No. 2-244188, uses a pseudo threedimensional display method in which a coordinate transformation of twodimensional map information is executed to generate a pseudo threedimensional image so as to display the map information in the vicinityof the current automobile location in a more easily recognizable manner.The pseudo three dimensional display may give a kind of threedimensional impression to a viewer using the two dimensional mapinformation because, in the pseudo three dimensional display, a viewpoint is set at a predetermined position above the automobile, and aperspective image viewed along a viewing direction which makes an acuteangle with respect to the ground plane is displayed.

[0006] The pseudo three dimensional display of the prior art isgenerated from the two dimensional map information using the view pointdetermined while assuming a flat ground surface. This may cause someproblems if the stereoscopic map display method mentioned above isexecuted using three dimensional map information including informationregarding a topographical elevation, instead of the two dimensional mapinformation.

[0007] Namely, the three dimensional map information containstopographical information such as elevations of mountains, buildings orthe like. If such three dimensional information is used and the viewpoint is established with respect to the ground plane at sea level(altitude of 0 m) in the same way as that of the pseudo threedimensional display method, the established view point may end up insidea mountain which protrudes above the ground plane, depending on itsheight. If that is the case, the navigation system may not be able todisplay a location of the automobile or carry out the navigationprocedure.

SUMMARY OF THE INVENTION

[0008] The present invention is invented in light of the above mentionedproblems, and has an object to provide a map display method andapparatus which enable a stereoscopic map display using threedimensional map data including information indicating horizontallocations of map constituent elements such as topographical features,roads, buildings, and information indicating heights or elevations oraltitudes of at least some of the map constituent elements which arelocated in at least a part of the available horizontal map area.

[0009] Another object of the present invention is to provide anavigation system having a stereoscopic map display function whichenables renewal of contents of the display smoothly with movement of avehicle even with the topographic variation or ups and downs of roads.

[0010] The above objects of the present invention are accomplished by amap display method in which map information in an area specified inresponse to a current location of a moving object is read from a mapdatabase; a perspective map viewed from a view point toward a groundplane is generated by executing coordinate transformation procedures onthe map information; and a scenery image corresponding to theperspective map is displayed on a display device, wherein the view pointfor generating the perspective map is established above a height of amap constituent element existing at a location specified in response tothe current location of the moving object, and the height of the viewpoint is renewed with movement of the moving object.

[0011] Further, the above objects of the present invention areaccomplished by a map display method in which a perspective map isgenerated using map information in an area specified in response to alocation indicated by input location information, and a scenery imagecorresponding the perspective map is displayed, wherein a map databasewhich contains the map information includes information regardingheights of map constituent elements existing at least in a part of theavailable map area; a view point for generating the perspective map isestablished above a height of a map constituent element existing at amap location specified in response to the location indicated by theinput location information when information regarding the height of theconstituent element is available; and the height of the view point isreestablished when new input information is provided.

[0012] Further, the above objects of the present invention areaccomplished by a map display apparatus in which a perspective map isgenerated from map information in an area specified in response to alocation indicated by input location information; and graphic data fordisplaying a scenery image corresponding the perspective map isoutputted; comprising a view point setting unit for establishing atleast a height of the view point among variables to be set to generatethe perspective map, and a display processing unit for generating thegraphic data for displaying the scenery image corresponding theperspective map generated in response to the view point set by the viewpoint setting unit, wherein the view point setting unit establishes aheight of the view point above an elevation of a topographical featureat a map location which is specified in response to the locationindicated by the input location information when information regardingthe elevation of topographical feature is available.

[0013] Further, the objects of the present invention are accomplished bya navigation system comprising a map database device, a current locationdetection device, a map display device for generating a perspective mapfrom map information in an area specified in response to the currentlocation of an automobile, and generating graphic data for displaying ascenery image corresponding the perspective map, and a display device,wherein the map display device comprises a view point setting unit forexecuting at least a setting procedure of the view point among variablesto be set for generating the perspective map, and a display processingunit for generating graphic data for displaying a scenery imagecorresponding to the perspective map generated in response to the viewpoint established by the view point setting unit, and the view pointsetting unit establishes a height of the view point above an elevationof a topographical feature at a map location which is specified inresponse to the detected current location of the automobile wheninformation regarding the elevation of a topographical feature isavailable.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram showing a construction of the navigationsystem in an embodiment of the present invention;

[0015]FIG. 2 is a block diagram showing a hardware construction of anoperation and processing unit 1-1 of FIG. 1;

[0016]FIG. 3 is a block diagram showing a functional construction of theoperation and processing unit 1-1 of FIG. 1;

[0017]FIG. 4 is an explanatory illustration showing an example of astereoscopic display according to a display method of the presentinvention;

[0018]FIG. 5 is a block diagram for illustrating data flows in thedisplay method of the present invention;

[0019]FIG. 6 is an explanatory illustration showing a concept of thecoordinate transformation in the map display;

[0020]FIG. 7 is a flowchart for illustrating a view point settingmethod, which is a feature of the present invention;

[0021]FIG. 8 is an explanatory illustration for supplementing FIG. 7;

[0022]FIG. 9 is a flowchart for illustrating the view point settingmethod which changes a line of sight according to movement of thevehicle;

[0023]FIG. 10 is a flowchart for illustrating the view point settingmethod which fixes a height of the view point when an area has an almosta flat topographical feature;

[0024]FIG. 11 is an explanatory illustration showing a concept of theview point setting method which establishes the view point inside of thevehicle;

[0025]FIG. 12 is an explanatory illustration showing an example of thedisplay when the view point is set inside the vehicle;

[0026]FIG. 13 is a flowchart for illustrating the view point settingmethod which switches the view point to inside or outside of the vehicleaccording to a height of the view point;

[0027]FIG. 14 is a flowchart for illustrating the view point settingmethod which switches the view point to inside or outside of the vehicleaccording to a scale of the display;

[0028]FIG. 15 is a flowchart for illustrating the view point settingmethod which varies a view angle according to a view angle selection ofNormal/Wide;

[0029]FIG. 16 is a flowchart for illustrating the view point settingmethod which varies a height of the view point according to a displaymethod selection of the pseudo three dimensional display/the threedimensional display;

[0030]FIG. 17A is an explanatory illustration showing relative locationsof the vehicle and the view point in the three dimensional display;

[0031]FIG. 17B is an explanatory illustration showing relative locationsof the vehicle and the view point in the pseudo three dimensionaldisplay;

[0032]FIG. 18 is a flowchart for illustrating the view point settingmethod which varies a height of the view point according to a selectionof Scroll or not;

[0033]FIG. 19 is an explanatory illustration showing an example of adata format of the map database according to the present invention;

[0034]FIG. 20 is a flowchart for illustrating the view point settingmethod which varies a height of the view point according to whetherinformation regarding elevations of the topographical features areavailable or not;

[0035]FIG. 21 is a flowchart for illustrating the view point settingmethod which varies a height of the view point according to whetherinformation regarding elevations of the roads are available or not;

[0036]FIG. 22 is an explanatory illustration for supplementing FIG. 21;

[0037]FIG. 23A is an display example of the vehicle when the view pointis set at a higher position;

[0038]FIG. 23B is an display example of the vehicle when the view pointis set at a lower position; and

[0039]FIG. 24 is a block diagram showing a construction of a map displayapparatus in another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] An embodiment of the present invention will now be described withreference to the figures.

[0041] As shown in FIG. 1, a navigation system according to theembodiment comprises, for example, an operation and processing unit 1-1,a display device 1-2, a map database unit 1-3, a voice input/outputdevice 1-4, and an input device 1-5.

[0042] The operation and processing unit 1-1 is a main unit for variousprocessing such as detecting a current location of the vehicle based onoutput information from sensors 1-7-1-10 which will be described later,graphically developing a map image from the map information which isnecessary for the display and read from the map database unit 1-3 incorrespondence with the detected current location of the vehicle, andsuperposing a vehicle symbol on the map image for indicating the currentlocation of the vehicle which is detected by the sensors 1-7-1-10; orcalculating the best fitted route to a location requested by a user viathe input device 1-5 (for example, from the current location to adesignated destination), and guiding the user along the best fittedroute using the voice input/output device 1-4 and/or the display device1-2.

[0043] The display device 1-2 is a unit for displaying the graphicinformation generated in the operation and processing unit 1-1, andcomprises a CRT or a liquid crystal display device or the like.Typically, an RGB signal or NTSC (National Television System Committee)signal is used for a SI signal connecting the operation and processingunit 1-1 and the display device 1-2.

[0044] The map database unit 1-3 comprises a storage medium with a largecapacity such as CD-ROM, a IC card or DVD (Digital Video Disc), andcarries out read/write processing of the necessary map data. The voiceinput/output device 1-4 transforms a message for the user, which isgenerated by the operation and processing unit 1-1, to a voice signaland outputs the voice signal, as well as recognizing a user's voice andtransferring its content to the operation and processing unit 1-1.

[0045] The input device 1-5 is a unit for accepting various operationcommands, which will be described later, from the user, and compriseshardware switches such as a scroll key for scrolling the displayed map,a scale change key for changing a scale of the displayed map, ajoystick, and a touch panel disposed on the display screen.

[0046] The system of the embodiment further comprises sensors to be usedfor detecting a current location of the vehicle in a moving vehiclenavigation operation, such as a wheel rotation speed sensor 1-7 formeasuring a distance by multiplying a detected rotation rate of thewheel by a circumference of the wheel; an azimuth sensor 1-8 fordetecting an azimuth on which the vehicle is heading by measuring ageomagnetic field of the earth; a gyro sensor 1-9 for detecting arotation angle of the vehicle comprising an optical fiber gyro or anoscillating gyro; a GPS receiver 1-10 for determining the currentlocation, the heading direction and the heading azimuth of the vehicleby receiving signals from three or more GPS satellites simultaneouslyand measuring ranges and range rates between the vehicle and the GPSsatellites.

[0047] The system of the embodiment further comprises a trafficinformation receiver 1-11 for receiving signals from an FM multiplexbroadcast station or a beacon transmitter which transmits a trafficinformation signal regarding traffic congestion, road construction orroad closures, available parking, and the like. Further, the systemcomprises a vehicle LAN device 1-6 for receiving various informationabout the vehicle status such as open/close of doors, status and typesof the lights which are turned on, status of engine, and a result of aproblem diagnosis operation.

[0048]FIG. 2 shows an example of a hardware structure of the operationand processing unit 1-1.

[0049] The operation and processing unit 1-1 comprises the followingdevices which are interconnected to each others through a bus. Theseconstituent devices are a CPU 2-1 executing various operations such as anumerical operation or a control of the devices, a RAM 2-2 storing mapdata or operation data, a ROM 2-3 storing programs or data, a DMA(Direct Memory Access) 2-4 for executing a high speed data transferbetween the memories and between the memory and the device, a graphiccontroller 2-5 executing various graphic imaging operations such asdevelopment of vector data to pixel information and control of thedisplay operation, a VRAM 2-6 storing graphic image data, a colorpalette 2-7 converting the image data to the RGB signal, an A/Dconverter 2-8 converting an analog signal to a digital signal, a SCI 2-9converting a serial signal to a bus-synchronized parallel signal, a PIO2-10 sending the signal on the bus while synchronizing with the parallelsignal, and a counter 2-11 accumulating a pulse signal.

[0050]FIG. 3 shows a functional structure realized by the operation andprocessing unit 1-1 having the hardware structure mentioned above. Eachof the functional blocks will now be described.

[0051] A current location detection unit 3-5 executes operations toobtain a location of the vehicle after its movement (X′,Y′) from aninitial location (X,Y) using range and angle data obtained byintegrating range pulse data S5 measured at the wheel rotation speedsensor 1-7 and angular acceleration data S7 measured at the gyro 1-9,and further time-integrating these data. Further in the locationcalculation unit 3-5, the absolute azimuth on which the vehicle isheading is corrected using the azimuth data S6 from the azimuth sensor1-8 and the angle data obtained by integrating the angular accelerationdata S7 from the gyro 1-9 so as to bring the rotation angle of thevehicle and the moving azimuth into agreement. Further, the currentlocation detection unit 3-5 may output information regarding the currentlocation of the vehicle, after executing an operation, which cancels outerrors accumulated in the data outputted from the above mentionedsensors due to their data integration operations, using location data S8which is periodically obtained at the GPS receiver at a certain periodwhen the location data S8 is available.

[0052] Information regarding the current location obtained in this waycontains errors originated in the sensor data. Thus, a map matchprocessing unit 3-6 is provided to further increase accuracy indetecting the current location of the vehicle. The map match processingunit 3-6 executes operations such as comparing road data, which isincluded in the map in the vicinity of the current location of thevehicle read by the data read unit 3-7, and a trajectory of the vehicleobtained from the current location detection unit 3-5, and correctingthe current location so that the corrected location gives the bestcorrelation between shapes of the road data and the vehicle'strajectory. In many cases, the map matching process enables fitting ofthe current location into a road on which the vehicle is actuallymoving, and thus outputting of a precise current location of thevehicle.

[0053] The information regarding the current location of the vehicle isstored in a trajectory memory unit 3-8 every time the vehicle has moveda certain distance. The trajectory data is used to generate a graphicimage for marking the trajectory of vehicle on roads of thecorresponding map, where the vehicle had traveled.

[0054] A command decoder unit 3-1 accepts requirements (commands) from auser through the input device 1-5, analyzes contents of therequirements, and controls each of the units so as to execute operationsin response to the contents. For example, when the user requests a routeguidance to a destination, the command decoder unit 3-1 requests adisplay processing unit 3-10 to carry out operations to display a mapfor setting the destination, and further requests a route calculationunit 3-2 to carry out operations to calculate a route from the currentlocation to the destination.

[0055] The route calculation unit 3-2 searches for a route between thedesignated locations from the map data using the Dijkstra algorithm orthe like, and stores the route in a route memory unit 3-3. The routecalculation unit 3-2 may calculate several types of routes such as theshortest route between the designated locations, a route which isreachable within the shortest travel time, and the most inexpensiveroute.

[0056] A route guidance unit 3-4 compares link information for the routeguiding stored in the route memory unit 3-3 with the current vehiclelocation information obtained in the current location detection unit 3-5and the map match processing unit 3-6, and guides the user by vocallynotifying whether or not to go straight or turn left/right using a voiceinput/output device 1-4 a predetermined period of time before thevehicle pass through an intersection, or superposing a mark indicating adirection in which the vehicle should be directed on the map displayedon a screen of the display device 1-2.

[0057] The data read unit 3-7 is operated to fetch and prepare map dataof a requested area from the map database unit 1-3.

[0058] The view point setting unit 3-11 is one of characteristicfeatures of the present invention, which establishes variables such as aview point, a line of sight, a view angle, which should be establishedfor the map display method of the present invention.

[0059] The display processing unit 3-10 receives the map data in thevicinity of a location which is requested to be displayed from the dataread unit 3-7, develops the map data into a graphic image using the viewpoint/the line of sight/the view angle established by the view pointsetting unit 3-11 and using a display scale, an imaging method, animaging azimuth designated by the command decoder unit 3-1, andtransfers the developed graphic image to the VRAM 2-6. A menu displayunit 3-9 accepts various requests output from the command decoder unit3-1, and transfers images of various types of menus or symbols which arerequested to the display processing unit 3-10 for superposing the imageson the displayed map.

[0060]FIG. 4 shows an example of the stereoscopic map display, which isdisplayed by the device of the present embodiment and in which a part ofthe map data such as topographical features, roads, etc. are graphicallydeveloped into an image to be displayed. There, 4-2 is a mountain drawnbased on the topographic elevation data (altitude data), 4-3 is roadswhich are line-drawn using a fixed width, and 4-4 is a symbol indicatingthe current location of the vehicle. The display example 4-1 isgenerated by reading out the map data in the vicinity of the currentlocation of the vehicle from the map database unit 1-3 based on thecurrent location of the vehicle output from the sensor system, anddisplaying a scenery image (perspective map) viewed from a view pointestablished above the vehicle in the air using a method of the presentinvention.

[0061]FIG. 5 shows an example of a data flow when a stereoscopic maplike the one in FIG. 4 is displayed.

[0062] The data read unit 3-7 reads out the map data in the vicinity ofthe vehicle's current location from the map database unit 1-3 based onthe current location of the vehicle detected at the current locationdetection unit 3-5. The view point setting unit 3-11 reads the currentlocation of the vehicle detected at the current location detection unit3-5 and the map data containing topographical features, roads, buildingsfrom the data read unit 3-7, and establishes variables such as the viewpoint, the line of sight, the view angle, etc. which should beestablished for the stereoscopic map display.

[0063] The display processing unit 3-10 carries out a coordinatetransformation of the map data in the vicinity of the vehicle accordingto the view point, the line of sight and the view angle established bythe view point setting unit 3-11, and generates the perspective mapimage to be displayed. The map match processing unit 3-6, which obtainsthe vehicle's current location with a higher accuracy and inputs theaccurate current location to the view point setting unit 3-11 and thedisplay processing unit 3-10 as shown in FIG. 3, is omitted here in FIG.5, assuming that the current location detection unit 3-5 can obtain thecurrent location of the vehicle with a high enough accuracy.

[0064] The coordinate transformation operation used in the displaymethod of the present embodiment will now be described with reference toFIG. 6.

[0065] A perspective map 6-6 is generated by projecting a topographicalfeature 6-2 situated above a ground plane 6-4 at sea level onto a screen(view plane) 6-3 disposed between the view point (view reference point)6-1 and the topographical feature 6-2 through a series of coordinatetransformations. The series of coordinate transformations comprise, forexample, the first transformation for transforming the map dataexpressed in an object coordinate to that of a world coordinate, thesecond transformation for transforming the result of the firsttransformation into a view point coordinate whose origin is set at theview point 6-1, and the third transformation for transforming the resultof the second transformation into a screen coordinate so as to projectthe result of the second transformation onto the screen 6-3.

[0066] According to the series of coordinate transformations, theperspective map 6-6 in a screen window corresponding to a part of thetopographic feature may be generated depending on a spatial relationshipbetween the view point 6-1 and the topographic feature 6-2. In thepresent embodiment, the display device 1-2 displays a graphic imagegenerated using data of the perspective map 6-6 so as to show scenery (ascenic image) which is supposed to be seen when a part of thetopographic feature 6-5 is viewed from above in the air.

[0067] In this specification, “the ground plane at sea level” means aflat plane like the plane 6-4 shown in FIG. 6, and “the ground plane”means a surface of the ground plane like 6-2.

[0068] An example of the procedure in the view point setting unit 3-11of the present embodiment will now be described with reference to FIGS.7 and 8. FIG. 7 is a flowchart of the procedure steps, and FIG. 8 is anexplanatory illustration for supplementing FIG. 7. In the following, alocation of the vehicle is assumed to be at a point 8-1.

[0069] First, the current location of the vehicle 8-1 is obtained fromthe current location detection unit 3-5 or through the map matchprocessing unit 3-6 (Step 7100). Then, a height (elevation) h_(t) at thecurrent location of the vehicle is calculated based on data regarding aheight of the topographical feature (elevation data), which are obtainedthrough the data read unit 3-7 (Step 7200). If the accuracy of data inthe height direction of GPS signal for detecting the current location ofthe vehicle is considered to be high enough, Step 7200 may be skipped.

[0070] Next, a predetermined height Y is added to the vehicle elevationh_(t) for calculating a view point height y_(v) so as to set the viewpoint above the vehicle elevation h_(t) (Step 7300). In the Step 7400,it is decided if the established view point is above the ground plane ornot by comparing the view point height y_(v) and an elevation h_(v) at alocation which is behind the vehicle's current location with apredetermined separation distance L.

[0071] If it is decided that the view point is above the ground plane (Yat Step 7400), the view point 8-2 is finally established behind thevehicle's current location with the predetermined separation distance Land at the height y_(v) (Step 7600), and the line of sight of the viewpoint is set toward the vehicle's current location 8-1 (Step 7700). Ifthe view point is located under the ground plane (N at Step 7400), y_(v)is reset so as its value becomes larger than h_(v) (Step 7500), and thenthe operation procedure moves to Step 7600.

[0072] As described above, the present procedure enables setting andresetting of the height of the view point so that the view point isalways located above in the air while the vehicle is moving.

[0073] Alternatively, the view point height y_(v) (y_(v)′ at a location8-3) may be set using a fixed height difference Y between the vehicleand the view point as the vehicle moves from the location 8-1 to thelocation 8-3 as shown in FIG. 8. This makes it possible to fix arelative spatial relationship between the vehicle's location and theview point.

[0074] According to the procedure shown in FIG. 7, the spatialrelationship may be maintained in a normal situation, and the locationof the view point may be set always above in the air by executing anexceptional step like Step 7500 even when there is a large amount of thetopographical variation.

[0075] It is obvious that the setting method of the view point height inthe present embodiment may be also applicable in the same way asmentioned above even when the topographical elevation or the roadelevation is less than sea level, i.e. even when the elevation valuesare less than zero.

[0076] Another embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 9.

[0077] In the present embodiment, procedure steps for displaying thevehicle and scenery around the vehicle while changing the view pointwith movement of the vehicle are added to the procedure of FIG. 7. Steps7110, 7210, 7710 of the present procedure are the same as Steps 7100,7200, 7700 of FIG. 7 respectively except that the current location ofthe vehicle in the present embodiment is assumed to be at the location8-3 of FIG. 8.

[0078] In the present procedure, the view point setting unit 3-11obtains the current location of the vehicle (Step 7110), calculates thevehicle elevation h_(t+dt) (Step 7210), obtains the previous view point8-2 (Step 7211), and calculates a distance d between the previous viewpoint 8-2 and the vehicle's current location 8-3 (Step 7212).

[0079] Further, it is decided if the distance d is within apredetermined range or not (Step 7213). If the distance d is within thepredetermined range (Y at Step 7213), the same view point is maintained(Step 7214), and only the line of sight is changed toward the newcurrent location of the vehicle (Step 7710). If the distance d is largerthan the predetermined range (N at Step 7213), the procedure proceeds toStep 7300 of FIG. 7.

[0080] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 10.

[0081] In the present embodiment, procedure steps for setting the viewpoint height while judging its necessity of renewal based on an amountof topographical variation around the vehicle's current location areadded to the procedure of FIG. 7. Steps 7110, 7210, 7710 of the presentprocedure are the same as Steps 7100, 7200, 7700 of FIG. 7 respectivelyexcept that the current location of the vehicle in the presentembodiment is assumed to be at the location 8-3 of FIG. 8.

[0082] In the present procedure, the view point setting unit 3-11obtains the vehicle's current location 8-3 (Step 7110), calculates thevehicle elevation h_(t+dt) (Step 7210), obtains the previous view pointheight y_(v) (Step 7211), calculates a height difference Δ h between thevehicle elevation h_(t+dt) at its current location and the height of theprevious view point (Step 7221), and checks if the height difference Δ his within a predetermined range or not (Step 7222).

[0083] If the height difference Δ h is within the predetermined range (Yat Step 7222), the same height of the view point as the previous one ismaintained and the new view point 8-4 is established with this height(Steps 7223, 7710). If not, the procedure proceeds to Step 7300 of FIG.7.

[0084] The present procedure is required to be executed as the vehiclemoves. Instead of the present procedure, it may be possible to dividethe map into a plurality of meshes each having a predetermined map area,and to establish the view point height to a fixed value within each ofthe meshes by evaluating an amount of the topographical variation withinthe mesh. Alternatively, a section of roads where the view point heightmay be fixed may be specified beforehand by evaluating an amount of upsand downs of roads on which the vehicle is planning to travel.

[0085] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIGS. 11 and 12.

[0086] In the present embodiment, the view point, which was establishedabove in the air and behind the vehicle in the previous embodiments, isnow established inside the vehicle. Concretely, the height of the viewpoint 11-2 established inside the vehicle 11-1, which is moving on theground of elevation h from sea level, is determined by adding theelevation h of the vehicle's current location and a predetermined heightYi. The view point established inside the vehicle will be called aninside-vehicle view point hereafter.

[0087] The procedure in the present embodiment is basically the same asthat of FIG. 7 with the predetermined height Y being replaced with Yi inStep 7300, and makes it possible to establish the inside-vehicle viewpoint. Further in the present embodiment, Steps 7400 and 7500 of FIG. 7may be eliminated since the view point is always set above the groundplane at Step 7300.

[0088] Alternatively, the height Yi may be defined as a variable so thatits value may be adjusted in response to the type of vehicle or avehicle height which is inputted or selected by the user using the inputdevice 1-5.

[0089]FIG. 12 illustrates an example 12-1 of the display showing ascenery image near an intersection with the inside-vehicle view point.The display example 12-1 also shows a part of the vehicle structure,which may be seen by the driver (user) when he or she is looking outfrom the inside of the vehicle, such as a front glass frame 12-2 andrear view mirror 12-3, superimposed on the scenery image. The part ofvehicle structure may be graphically generated using its structural datawhich may be stored in a storage device such as the map database device1-3 or the ROM 2-3.

[0090] Displaying the part of the vehicle structure superposed on thescenery image enables the user to relate an actual view from inside thevehicle and the displayed roads and buildings more easily, and thusincrease the recognizability. Alternatively, the navigation system maybe structured in such a way that the input device 1-5 accepts the user'sselection regarding which part of the vehicle structure should bedisplayed, and the display image is generated according to the user'sselection. Further, the display with more clarity may be realized byadditionally executing transparent processing during the displayprocedure.

[0091] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 13.

[0092] The procedure of the present embodiment includes steps, inaddition to the procedure illustrated in FIG. 7, for switching alocation of the view point between inside and outside the vehicledepending on a view point height requested by the user. Further in thepresent embodiment, the input device 1-5 is structured so as to be ableto accept a selection or switching operation from the user for changingthe view point height stepwise.

[0093] In the present procedure, the view point height y_(v) requestedby the user is obtained (Step 1310), and then it is checked if the viewpoint height y_(v) is less than a predetermined height Y1 (Step 1320).If it is less than Y1, the view point height y_(v) is established insidethe vehicle using the method described with reference to FIG. 11 (Step1330), and the line of sight is set along the moving direction of thevehicle (Step 1340).

[0094] If the view point height y_(v) is not less than Y1 in Step 1320,the view point height y_(v) is further checked to see if it is largerthan another predetermined height Y2 (Step 1350). If it is larger thanY2, the line of sight is set in a direction vertical to the ground planeat sea level 6-4 (Step 1360). If the view point height y_(v) is not lessthan Y1 and not larger than Y2, the view point height and a direction ofthe line of sight are determined using Steps 7200-7700 of FIG. 7.

[0095] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 14.

[0096] The procedure of the present embodiment includes steps forswitching a location of the view point between inside and outside thevehicle depending on a map display scale requested by the user, inaddition to the procedure illustrated in FIG. 7. Further in the presentembodiment, the input device 1-5 is structured so as to be able toaccept a selection or switching operation from the user for changing themap display scale stepwise. Further, Steps 1430, 1440, 1460 in thepresent procedure are the same as Steps 1330, 1340, 1360 in theprocedure shown in FIG. 13, respectively.

[0097] In the present procedure, the display scale s requested by theuser is obtained (Step 1410), and then the display scale s is checked tosee if it is less than a predetermined scale S1 (Step 1420). If it isless than S1, the view point height y_(v) is established inside thevehicle using the method described with reference to FIG. 11 (Step1430), and the line of sight is set along the moving direction of thevehicle (Step 1440).

[0098] If the display scale s is not less than S1 in Step 1420, thedisplay scale s is further checked to see if it is larger than anotherpredetermined scale S2 (Step 1450). If it is larger than S2, the line ofsight is set in a direction vertical to the ground plane at sea level6-4 (Step 1460). If the display scale s is not less than S1 and notlarger than S2, the view point height and a direction of the line ofsight are determined using Steps 7200-7700 of FIG. 7.

[0099] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 15.

[0100] The procedure of the present embodiment includes steps which makeit possible to switch a view angle for displaying the map according to auser request regarding variables such as a display format of the displaydevice 1-2, in addition to the procedure illustrated in FIG. 7. Furtherin the present embodiment, the input device 1-5 is structured so as tobe able to select either a wide display mode or a normal display modefor setting the view angle of the display.

[0101] First, in the present procedure, the view angle requested by theuser is obtained (Step 1510), and a value of the view angle is checkedso as to decide whether the display mode should be in the wide mode orthe normal mode (Step 1520). If the normal display mode is selected, theview angle is set at a default value (Step 1530). If the wide displaymode is selected, the view angle is set to a larger value than thedefault view angle (Step 1540). The procedure then proceeds to Step 7200of FIG. 7 for determining the view point height and a direction of theline of sight.

[0102] The display size may be changed to a wider shape, for example,like the display example 12-1 shown in FIG. 12. Further, the switchingprocedures illustrated in FIGS. 13 and 14 for switching the view pointbetween inside and outside the vehicle may be utilized in the presentprocedure so as to change the view angle in response to the switching ofthe view point location.

[0103] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIGS. 16, 17A and 17B.

[0104] The procedure of the present embodiment includes steps forswitching the view point in response to switching of the display methodbetween a three dimensional display and a pseudo three dimensionaldisplay according to the user request, in addition to the procedureillustrated in FIG. 7. In the present specification, the threedimensional display method means a method for displaying a stereoscopicthree dimensional map using the map information containing heightinformation such as the elevation or the like, and the pseudo threedimensional display method means a method for generating a map imagefrom the two dimensional map information through the perspectivetransformation so as to display the map which makes it possible to givea distinctive impression of distance.

[0105] Further in the present embodiment, the input device 1-5 isstructured so as to be able to accept a request from the user forselecting either one of the three dimensional display and the pseudothree dimensional display. Step 7710 of the present procedure is thesame as Step 7700 of FIG. 7.

[0106] In the present procedure, the display method requested by theuser is obtained (Step 1610), and it is then decided if the displayshould be executed by the three dimensional display method or the pseudothree dimensional display method (Step 1620). If the three dimensionaldisplay method is selected, the procedure proceeds to Step 7200 of FIG.7. There, as shown in FIG. 17A, the view point height y_(v) isdetermined based on the topographic elevation h_(t) at the vehicle'scurrent location 8-3 and the predetermined height Y, and the view point8-4 is set at a location behind the vehicle separated by thepredetermined distance L with the view point height determined by Steps7200-7700. If the pseudo three dimensional display method is selected,the view point 17-2 is set at a location behind the vehicle's currentlocation 17-1 separated by the predetermined distance L and thepredetermined height Y above sea level (Step 1630), and the line ofsight is set along a direction toward the vehicle from the establishedview point (Step 7710).

[0107] The display processing unit 3-10 generates graphic data fordisplaying a perspective map viewed from the view point established inthe above procedure using the display method selected by the user, andoutputs the graphic data to the display device 1-2.

[0108] Alternatively, the procedure may be structured so that the heightY above sea level 6-4 may be switched to a fixed value during theswitching of the display method in the present procedure.

[0109] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIG. 18.

[0110] The procedure of the present embodiment includes steps forswitching the view point to a location 8-4 or 17-2 of FIGS. 17A and 17Bin response to a scroll request from the user, in addition to theprocedure illustrated in FIG. 7. Further in the present embodiment, theinput device 1-5 is structured so as to be able to accept a scrollrequest operation entered by the user. Step 7110 in the presentprocedure is the same as Step 7100 of FIG. 7.

[0111] In the present procedure, the vehicle's current location isobtained (Step 7110), and then it is decided if the user requests thescroll operation (Step 7111). If the scroll operation is requested, theview point 17-2 is set as shown in FIG. 17B at a predetermined heightabove the ground plane at sea level (Step 7112), and the line of sightfrom the view point is set along the scrolling direction (Step 7113).

[0112] In the present embodiment, the view point setting unit 3-11establishes the view point height with respect to sea level when ascroll button disposed in the input device 1-5 is being pressed. Aprocessing speed for renewing the display image may be graduallyincreased when the scroll button is kept pressed. Alternatively, theprocedure may be structured so that a scroll speed or an elapse of timesince the scroll button has been pressed may be checked if it is beyonda corresponding predetermined value in Step 7111 when the display iscontrolled in such a way that the display image is renewed at a constantperiod, and the above switching procedure may be executed if the scrollspeed or the elapse of time is beyond the corresponding predeterminedvalue.

[0113] An example of data structure in the map database device 1-3 ofthe present invention will now be described.

[0114] Map data of the present example comprises a data management unit19-1 and a data unit 19-2 as illustrated in FIG. 19. The map data may bemanaged, for example, using a “standard area mesh” which is obtained bydividing a total area with longitude and latitude lines separated fromeach other by fixed amounts. An identification number called a mesh codeis given to each of the standard area mesh.

[0115] The data management unit 19-1 stores a plurality of managementtables each corresponding to a respective one of the standard areameshes. Each of the management table stores the mesh code 19-3,attribute information 19-4, an elevation data management unit 19-5, aroad data management unit 19-6, a building data management unit 19-7,and the like.

[0116] The attribute information 19-4 stores a scale of the map, a dateof the map data generation, and a number/name of the map. The elevationdata management unit 19-5 stores link destinations in an elevation data19-8. The elevation data 19-8 comprises elevation values sampled atlocations which are equally separated from each other in the standardarea mesh, and makes it possible to generate a display image of itstopographical feature.

[0117] The road data management unit 19-6 stores link destinations in aroad data 19-9 in a similar way. The road data 19-9 stores linkinformation connecting intersections (nodes), node coordinates,attribute information identifying a type of road such as a toll road ora national road, road height information, and the like. Further, thebuilding data management unit 19-7 stores link destinations in buildingdata 19-10. The building data 19-10 stores information such as names,shapes, and heights of the buildings.

[0118] Further, identification codes will be stored for indicatingavailability of no link destination in the road/building elevationinformation stored in one of the data management units 19-5-19-7 and thedata 19-8-19-10 due to the lack of the corresponding data.

[0119] A further embodiment of the procedure of the view point settingunit 3-11 of the present invention will now be described with referenceto FIGS. 20-22.

[0120] The procedure of the present embodiment includes steps forswitching the view point in response to the above describedidentification codes, which may be obtained by utilizing the mapdatabase device 1-3 with the data structure described in FIG. 19, inaddition to the procedure illustrated in FIG. 7.

[0121]FIG. 20 shows an example of the procedure for switching the viewpoint in response to detection of elevation information of thetopographic feature (elevation data). Steps 7110, 7710 and 7123 in thepresent procedure are the same as Steps 7100, 7700 of FIG. 7 and Step1630 of FIG. 16 respectively.

[0122] In the present procedure, the map management information19-3-19-7 of the standard area mesh corresponding to an area in thevicinity of the vehicle's current location are fetched from the mapdatabase device 1-3, and contents of the map management information areobtained (Step 7121). Further, it is decided if the elevationinformation of topographical feature is available or not in thecorresponding standard area mesh by checking the elevation datamanagement unit 19-5 of the obtained map information (Step 7122).

[0123] If the elevation information of topographic feature is available,the procedure proceeds to Step 7200 of FIG. 7, and establishes the viewpoint and the line of sight for the three dimensional display accordingto Steps 7200-7700. If the elevation information of topographic featureis not available, the procedure proceeds to Step 7123 to set the viewpoint for the pseudo three dimensional display at the location 17-2 ofFIG. 17B and the line of sight along a direction toward to the vehicle(Step 7710).

[0124]FIG. 21 illustrates an example of the procedure for switching theview point in response to detection of the elevation information of theroad. FIG. 22 is an explanatory illustration supplementing FIG. 21. Theprocedure of the present embodiment includes Steps 7231, 7232 inaddition to the procedure illustrated in FIG. 7. In the presentprocedure, these additional steps are placed after Step 7200 of FIG. 7,and the vehicle is assumed to be located at a location 22-1 of FIG. 22.

[0125] In the present procedure, it is decided if the elevationinformation of road is available or not by checking the road data 19-9included in the obtained map information at the vehicle's currentlocation 22-1 (Step 7231). If the road elevation hd 22-3 is available,the view point height yv is calculated from the road elevation hd, thetopographic elevation h and the predetermined height Y (Step 7232), andthe view point 22-2 is established behind the vehicle with thepredetermined separation L. If the road elevation hd is not available,the view point is established according to Steps 7300-7700.

[0126] Alternatively, when data from a plurality of meshes aresimultaneously developed into a display image, the procedure may bestructured so as to set the view point 1.7-2 for the pseudo threedimensional display if the mesh with no elevation data of topographicfeature is included.

[0127] Further, if the map database includes identification informationfor identifying a section of a road which is located inside a tunnel,the procedure may be structured so as to switch the view point to theinside-vehicle view point using the identification information fordeciding when the road section where the vehicle is currently moving isidentified as inside the tunnel.

[0128] A further embodiment of the map display method of the presentinvention will be described with reference to FIGS. 23A and 23B.

[0129] In the present embodiment of the map display method, ashape/color/pattern/size of the vehicle's display image is varied inresponse to a change in the display setting condition such as the viewpoint, the line of sight, the view angle and the like.

[0130] To be concrete, the vehicle symbol may be displayed in a simpleform as shown in FIG. 23A when the view point is set at a higher ordistant location to the vehicle, and displayed in a stereoscopic form asshown in FIG. 23B when the view point is set at a lower or closerlocation to the vehicle.

[0131] The above process may be realized by switching structural data ofthe vehicle symbol to be used, for example, according to a result of thedecision at Step 1320 or 1350 in FIG. 13. Further, the display form ofthe vehicle symbol may be changed in response to the switching of thedisplay method between the three dimensional display and the pseudothree dimensional display if the change of the vehicle's display form isexecuted depending on a result of the decision at Step 1620 in FIG. 16.

[0132] According to the present invention as described above, the mapdata including topographic features, roads, and buildings in thevicinity of the current location of the vehicle is read from the mapdatabase as the vehicle moves, and the view point is continuouslyrenewed so as to be established at a point which is higher than theelevation of topographic feature in the vicinity of the vehicle'scurrent location. Therefore, it is possible to provide the navigationsystem which makes it possible to maintain the view point above theground surface even with the topographical variation, and renew thescenery image smoothly with the vehicle's motion.

[0133] In the above mentioned embodiments, the map display methodsemployed in the navigation system with the structure shown in FIG. 1 aredescribed as examples. However, the map display method of the presentinvention is not limited to these embodiments. For example, a system maybe realized by storing programs for executing the map display method instorage media such as floppy disks, CDs or the like, and loading theprograms into a conventional computer system for executing the loadedprograms.

[0134] Concretely, a map display apparatus may be realized for executingvarious map display methods mentioned above by storing a map displayprogram for executing the map display method of the present inventioninto a storage medium 24-2, and loading the map display program into acomputer system comprising a central operation and processing device24-1, a display 24-5 and an input device 24-6 for executing the mapdisplay program. There, the map database 24-3 is connected to thecomputer system for providing map information, and location information24-4 indicating a location to be displayed is fed to the computersystem. The location information may be provided, for example, from aGPS card which is connected to a computer and functions as a GPSreceiver.

[0135] In the above embodiments, the navigation system for an automobileis assumed as an example of the present invention. However, the presentinvention is also applicable to a portable navigation system for othertypes of moving object such as a person, who may use the system duringtrekking or the like in the same way as the previous embodiments.

[0136] According to the present invention, it is possible to provide amap display method and apparatus which makes it possible to display astereoscopic map image based on three dimensional map information.

[0137] Further, according to the present invention, it is possible toprovide a navigation system having a function to display a stereoscopicmap image, which makes it possible to renew a scenery image smoothlywith movement of the vehicle, regardless of topographic variation.

What is claimed is:
 1. A map display method in which map information inan area specified in response to a current location of a moving objectis read from a map database; a perspective map looking from a view pointtoward a ground plane is generated by executing coordinatetransformation procedures on said map information; and a scenery imagecorresponding to said perspective map is displayed on a display device,wherein said view point for generating said perspective map isestablished above a height of a map constituent element existing at alocation specified in response to the current location of said movingobject, and said height of said view point is renewed with movement ofsaid moving object.
 2. A map display method in which map information inan area specified in response to a location indicated by an inputlocation information is read from a map database; a perspective maplooking toward a ground plane from a view point is generated using saidobtained map information; and a scenery image corresponding to saidperspective map is displayed on a display device, wherein said mapdatabase includes information regarding heights of map constituentelements existing at least in a part of an available map area, said viewpoint for generating said perspective map is established above a heightof a map constituent element existing at a map location specified inresponse to said location indicated by said input location informationwhen information regarding height of said constituent element isavailable, and said height of said view point is reset when a new inputinformation is provided.
 3. A map display apparatus connecting to a mapdatabase and a display device for displaying a map, in which mapinformation in an area specified in response to a location indicated byan input location information is read from the map database; aperspective map looking from a view point toward a ground plane isgenerated using said obtained map information; graphic data fordisplaying a scenery image corresponding to said perspective map isgenerated; and the graphic data is outputted to said display device,comprising a view point setting unit for setting at least a height ofsaid view point among variables to be set for generating saidperspective map, and a display processing unit for generating graphicdata for displaying a scenery image corresponding to said perspectivemap generated in response to said view point established by said viewpoint setting unit, wherein said map database includes informationregarding elevations of topographic features existing at least in a partof an available map area, and said view point setting unit establishes aheight of said view point above an elevation of a topographical featureat a map location specified in response to said location indicated bysaid input location information when information regarding saidelevation of a topographical feature is available.
 4. A map displayapparatus in accordance with claim 3, wherein said location indicated bysaid input location information is a current location of a movingobject, and said view point setting unit repeats its view point settingprocedure when renewed location information is provided with movement ofsaid moving object.
 5. A map display apparatus in accordance with claim4, wherein said view point setting unit establishes said view pointabove in the air behind said moving object while keeping a predeterminedrelative relationship to a current location of the moving object, whichis renewed constantly.
 6. A map display apparatus in accordance withclaim 4, wherein said view point setting unit keeps the previous viewpoint position, and reestablishes a line of sight so as to be able tocapture said moving object in the current location within its field ofview if a relative spatial relationship between the newly-providedcurrent location of said moving object and the previously-establishedview point satisfies a predetermined condition range.
 7. A map displayapparatus in accordance with claim 4, wherein said view point settingunit fixes the height of said view point when said moving object islocated within a section of area which is specified in response to apredetermined range if an amount of topographic variation in an areawhich extends as much as said predetermined range from the currentlocation of said moving object is not larger than a predetermined value.8. A map display apparatus in accordance with claim 4, wherein saidmoving object is an automobile, and said view point setting unitestablishes said view point for generating said perspective map lookingfrom inside of said automobile with an elevation of a topographicalfeature at the current location of said automobile and a height of saidautomobile's body.
 9. A map display apparatus in accordance with claim4, further comprising input means for accepting requests from a userregarding the height of said view point to be set, wherein said movingobject is an automobile, and said view point setting unit establishes;said view point inside of said automobile, and a line of sight toward amoving direction of said automobile when said requested height of saidview point is not larger than a predetermined value; said view pointabove in the air behind said automobile, and said line of sight along adirection toward said automobile from said established view point whensaid requested height of said view point is within a predeterminedrange; said line of sight vertically from said view point established inresponse to said requested height of said view point so as to view theground plane at sea level directly below when said requested height ofsaid view point is larger than a predetermined value.
 10. A map displayapparatus in accordance with claim 4, further comprising input means foraccepting requests from a user regarding a display scale to be set,wherein said moving object is an automobile, and said view point settingunit establishes; said view point inside of said automobile, and a lineof sight toward a moving direction of said automobile when saidrequested display scale is not larger than a predetermined value; saidview point above in the air behind said automobile, and said line ofsight along a direction toward said automobile from said establishedview point when said requested display scale is within a predeterminedrange; said line of sight vertically from said view point established inresponse to said requested height of said view point so as to view theground plane at sea level directly below when said requested displayscale is larger than a predetermined value.
 11. A map display apparatusin accordance with claim 4, further comprising input means for acceptingrequests regarding a view angle to be set for generating saidperspective map, wherein said display processing unit sets a value of aview angle to one of a predetermined normal value and a wide valuelarger than said normal value according to said accepted request, andgenerates graphic data for displaying said perspective map in accordancewith said established view angle.
 12. A map display apparatus inaccordance with claim 4, further comprising selection means foraccepting requests regarding a selection of a display method between apseudo three dimensional display method which makes it possible to givea distinctive impression of distance by executing perspectivetransformation procedures on two dimension horizontal data containingsaid map information, and a three dimensional display method whichdisplays a scenery image using three dimensional data containing saidmap information, wherein said view point setting unit establishes; saidview point at a predetermined height with respect to the ground plane atsea level when said pseudo three dimensional display method is selected,and said view point above an elevation of a topographic feature at a maplocation specified in response to the current location of said movingobject when said three dimensional display method is selected.
 13. A mapdisplay apparatus in accordance with claim 12, wherein said view pointsetting unit reestablishes a height of said view point so as not tochange a distance in the height direction from the ground plane to saidview point when said display method is changed by said selection meansbetween said pseudo three dimensional display method and said threedimensional display method.
 14. A map display apparatus in accordancewith claim 4, further comprising decision means for deciding ifinformation regarding the height of at least one of a topographicfeature, a road, and a building is included in said obtained mapinformation, wherein said view point setting unit establishes said viewpoint above an elevation of a topographic feature when said decisionmeans decides that information regarding said elevation of a topographicfeature is included in said map information, and establishes said viewpoint at a predetermined height with respect to the ground plane at sealevel when said decision means decides that information regarding saidelevation of a topographic feature is not included.
 15. A map displayapparatus in accordance with claim 4, further comprising decision meansfor deciding if information regarding the height of at least one of atopographic feature, a road, and a building is included in said obtainedmap information, wherein said view point setting unit establishes saidview point at a predetermined height with respect to the ground plane atsea level if a plurality of map meshes to be displayed are furtherincluded in said map information, and said decision means decides thatat least one of said map meshes contains no information regarding saidelevation of a topographic feature.
 16. A map display apparatus inaccordance with claim 4, wherein said display processing unit generatesgraphic data for displaying a graphic image illustrating said movingobject superposed on a scenery image to be displayed, and changes saidgraphic image of said moving object in response to a change of arelative spatial relationship between said established view point andsaid moving object due to a change in the setting condition of said viewpoint setting unit.
 17. A navigation system comprising a map databasedevice for storing map information at least including informationregarding topographical features and roads; a current location detectiondevice for detecting a current location of an automobile on which saidnavigation system is mounted; a map display device for fetching mapinformation in an area specified in response to said detected currentlocation of said automobile, generating a perspective map viewing theground plane from a view point using said obtained map information, andgenerating graphic data for displaying a scenery image correspondingsaid perspective map; and a display device for displaying a map imageaccording to said graphic data, wherein said map display devicecomprises a view point setting unit for executing at least settingprocedures of said view point among variables to be set for generatingsaid perspective map, and a display processing unit for generatinggraphic data for displaying a scenery image corresponding to saidperspective map generated in response to said view point established bysaid view point setting unit, said map database includes informationregarding the elevation of a topographic feature existing at least in apart of an available map area, and said view point setting unitestablishes a height of said view point above an elevation of atopographical feature at a map location which is specified in responseto said detected current location of said automobile when informationregarding said elevation of a topographical feature is available.
 18. Amap display apparatus in accordance with claim 17, further comprising auser interface for accepting requests to set at least one of a type anda height of said automobile, wherein said map display device establishessaid view point using said established variables in response to theaccepted request, and generates graphic data for displaying a sceneryimage corresponding to said perspective map generated using saidestablished view point.
 19. A map database storing map information whichcomprises plural types of information regarding map constituentelements, comprising at least information regarding heights of mapconstituent elements existed at least in a part of an available maparea, and information for identifying the availability of saidinformation regarding the heights.
 20. A medium storing programs forrealizing a map display method in which map information in an areaspecified in response to a location indicated by an input locationinformation is read from a map database; a perspective map looking froma view point toward the ground plane is generated using said obtainedmap information; and a scenery image corresponding to said perspectivemap is displayed on a display device, wherein said view point forgenerating said perspective map is established above a height of a mapconstituent element existing at a map location specified in response tosaid location indicated by said input location information wheninformation regarding said height of said constituent element isincluded in said map database, and said height of said view point isreset when new input information is provided.